scan-big-text-files.sh

# use grep to search the output of the file for specific terms.
# the `-n` flag will output line numbers to the left of matches.

cat some.log | grep -n "Looking for..."

# you can then use the line number to find the entries on and around the entry. 
# Note the line-number is used, as well as a count to includes a number of lines after.

# In this example, we're looking at lines starting at 3176101 and the +10 lines after.
sed -n '3176101,+10p' app.log 


# OTHER
# need a solid sed cheatsheet? Check this out: https://edoras.sdsu.edu/doc/sed-oneliners.html